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Tin sulfide (SnS) semiconductor has recently attracted a great deal of attention from the scientific community regarding its application in solar cells. However, SnS solar cell efficiencies are still limited to less than 5%. The incorporation of nanostructures into solar cells has been demonstrated to be a potential route to improve device performance. So far, there have been no reports on the incorporation of nanostructures into SnS solar cells. In this work, a theoretical study on the incorporation of tin sulfide selenide (SnSSe) nanostructures in the form of quantum wells (QWs) into SnS solar cells under the radiative limit is presented, for the first time. In particular, the impact of well number, well thickness, and Se/(S + Se) compositional ratio at the wells, on solar cell characteristics, is evaluated. An efficiency enhancement of 11.1% is found for a SnS/SnSSe QW solar cell, compared to the optimized device without nanostructures, for 50 wells of 54 nm width with a Se/(S + Se) well composition of 0.4 and considering barrier thicknesses of 5 nm, which is a result of the increase in short-circuit current density of 14.5%. The influence of defects at wells and barriers, as well as defects at interfaces, on solar cell behavior is also presented, demonstrating that the introduction of QWs can result in higher efficiencies than that of the device without nanostructures. In this sense, the addition of SnSSe nanostructures to SnS solar cells is introduced as a potential route to promote the absorption of photons with energy lower than the SnS band-gap, while keeping open-circuit voltage values similar to those of a SnS solar cell without nanostructures, thereby increasing solar cell efficiency.

In this work, a path to overcome the highest current efficiency on SnS thin-film solar cells by the Se incorporation is presented. We carried out a theoretical study of the effect of different Se/(S + Se) compositional ratios (CRs) (from 0.0 to 1.0) on the solar cell performance. In this sense, an improvement on power conversion efficiency (PCE) by decreasing the energy band gap (theoretical Se incorporation) from 1.35 to 1.08 eV was observed. All electrical output parameters (open-circuit voltage, short-circuit current density, fill factor and PCE) were increased by an augment of the CR from 0.25 to 0.75. A PCE of 10.23% was obtained for a CR of 0.75. Furthermore, a thickness optimization of the absorber was carried out, where the greatest PCE of 11.78% was obtained at 800 nm. On the other hand, a simulation at different work functions in back contact and different bulk defect density on the absorber were performed in order to achieve higher efficiencies.

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